在数组中添加数字。 得到奇怪的输出。 Java脚本

Question

    var array = [];        
    getNum();
    document.write(array);
    document.write("<br>Sum: " + sum(array));

    //Function to Sum Array
    function sum(params){
        var total = 0 ;
        for (i = 0; i < params.length; i++){
            total += params[i];
        }
        return total;
    }


    //Function to get Numbers in Array
    function getNum(){
        var count = 0;
        alert("Please enter 5 numbers");
        while(count < 5) {
            array[count] = prompt("Number " + (count + 1));
            count++;
        }
    }

Current Output

5,4,3,2,1
Sum: 054321

What I want

5,4,3,2,1
Sum: 15

I'm trying to make a program where the user adds numbers to an Array and the program calculates different things about those numbers.

When I call sum(array); with a preset array such as var array = [5,4,3,2,1]; The summing works fine and outputs 15 as expected.
However instead of having a preset array, when I include the function to get the set of numbers for the Array, the summation the output is 054321.

I want to do the array calculations manually for my own understandings sake, rather than using reduce();

What am I doing wrong?

Answer 1

Parse your prompt value as an integer - it's being added as a string and concatenated with the + sign:

array[count] = parseInt(prompt("Number " + (count + 1)));

http://jsfiddle.net/4kp825tc/

MDN also recommends to cast as a Number as another option:

Please note that result is a string. That means you should sometimes cast the value given by the user. For example, if his answer should be a Number, you should cast the value to Number. var aNumber = Number(window.prompt("Type a number", ""));

Answer 2

   //Function to Sum Array
    function sum(params){
        var total = 0 ;
        for (i = 0; i < params.length; i++){
            var temp = parseInt(params[i]);
            total += temp;
        }
        return total;
    }

Answer 3

Your inputs are stored as strings in your array. You'll need to convert the value to a number for the summation to occur correctly.

Use parseInt (set to base 10) to get the correct answer.

        total += parseInt(params[i],10);

http://jsfiddle.net/biz79/x9cbm7Lj/

Answer 4

The values from prompt are strings and thats why the don't add as you wish add plus before params[i] and your have it correct

var array = [];        
getNum();
document.write(array);
document.write("<br>Sum: " + sum(array));

//Function to Sum Array
function sum(params){
    var total = 0 ;
    for (i = 0; i < params.length; i++){
        total += +params[i]; //make the params[i] to be a number
    }
    return total;
}


//Function to get Numbers in Array
function getNum(){
    var count = 0;
    alert("Please enter 5 numbers");
    while(count < 5) {
        array[count] = prompt("Number " + (count + 1));
        count++;
    }
}

Answer 5

Here's a one-line solution:

function sum(params) {
    return params.map(function(item) { return parseInt(item); }).sum()
}

Answer 6

Do everything the same, just parse the user input to an integer. The issue here is that the numbers are being treated as strings.

Modify your sum function like this:

//Function to Sum Array
function sum(params){
    var total = 0 ;
    for (i = 0; i < params.length; i++){
    $num = parseInt(params[i]);
    total += $num;
    }
    return total;
}

That's it, you're done.